31 Years NEET Previous Year Questions: Structural Organisation in Animals

In frogs two distinct portal systems are present: the hepatic portal system (veins from intestine to liver) and the renal portal system (veins from the hind parts of the body to the kidneys).
The renal portal system carries blood from the hind limbs and lower body towards the kidneys so that nitrogenous wastes and other substances can be processed before blood returns to the heart; therefore option (b) is correct.

In water: Aquatic respiration in frogs is primarily through the skin (cutaneous respiration) and through the buccal cavity; lungs are not effectively used underwater. So the statement as given is false for the aquatic condition.
On land: Frogs use the skin, buccal cavity and lungs for gas exchange. Pulmonary respiration (by lungs) becomes important on land, so the statement is true for terrestrial condition — hence option (a) is correct.
During hibernation and aestivation, gas exchange is largely cutaneous (through the skin) and slowed down to conserve energy.

The systemic veins returning deoxygenated blood from the body to the heart are collectively called the vena cava (superior and inferior vena cava in vertebrates). In frogs, major veins open into the sinus venosus and right atrium via the venae cavae.
Thus (b) Vena cava is the correct choice. (Pulmonary veins carry oxygenated blood from lungs to heart; pulmonary arteries carry deoxygenated blood from heart to lungs; aorta distributes oxygenated blood from heart to body.)

Male frogs show sexual dimorphism. One diagnostic feature is a specialised thickened pad (the copulatory pad) on the first digit of the forelimb.
This pad helps the male grip the female during amplexus (mating). Female frogs lack this specialised first digit. Hence option (b) is correct.

The correct answer is Option B.
Anal cerci in both male and female cockroaches are located at the base of the 10th abdominal segment of their bodies. The cerci are a pair of long, filamentous, sensory appendages that help cockroaches detect movements in the air, which warns them of approaching threats from behind, such as predators. This placement provides an effective mechanism for detecting environmental changes directly around the cockroach's posterior, enhancing their ability to quickly respond and escape threats. The location on the 10th segment is typical and consistent in all cockroaches across different species.

To match List I (types of epithelium) with List II (examples where these epithelia are found), we need to understand the characteristics and common locations of each type of epithelial tissue.

Here's the clarification for each match:

Unicellular glandular epithelium: This refers to single cells that function as glands, such as goblet cells. They are typically found in epithelial linings where they secrete mucus; within the digestive tract, goblet cells are common components.

Compound epithelium: This type is characterized by multiple layers of cells and is primarily protective. Common examples include skin and the inner lining of the mouth which needs protection against mechanical and chemical stress.

Multicellular glandular epithelium: This is found in glands composed of many cells. Examples include the salivary glands, pancreas, etc., where multiple cells work together to produce and secrete substances like enzymes and saliva.

Endocrine glandular epithelium: These glands are ductless and release hormones directly into the blood. An example of such a gland is the pancreas, which not only acts as an exocrine gland by producing digestive enzymes but also functions endocrinologically by regulating blood sugar levels through insulin and glucagon production.

Based on the above understanding:

• A (Unicellular glandular epithelium) matches with III (Goblet cells of alimentary canal).
• B (Compound epithelium) matches with IV (Moist surface of buccal cavity).
• C (Multicellular glandular epithelium) matches with I (Salivary glands).
• D (Endocrine glandular epithelium) matches with II (Pancreas).

Thus, the correct answer is Option C: A-III, B-IV, C-I, D-II

The digestive system of a cockroach consists of several specialized structures that perform specific functions:
Crop is a part of the alimentary canal where food is stored temporarily. This aligns with the description for List I "A. The structures used for storing of food". Thus, A corresponds to IV (Crop).
Gastric Caeca are blind tubules located at the junction of the foregut and the midgut in insects. These tubules secrete enzymes and provide an increased surface area for digestion and absorption. This fits the description for List I "B. Ring of 6-8 blind tubules at junction of foregut and midgut". Hence, B corresponds to II (Gastric Caeca).
Malpighian tubules are thin filamentous structures present at the junction of the midgut and hindgut. They are primarily involved in excretion and osmoregulation. They match the description for List I "C. Ring of 100-150 yellow coloured thin filaments at junction of midgut and hindgut". Thus, C corresponds to III (Malpighian tubules).
Gizzard, also known as the proventriculus, is equipped with hard chitinous plates that grind the food mechanically. This description fits List I "D. The structures used for grinding the food". Therefore, D corresponds to I (Gizzard).
By collaborating all this information, the correct answer is: Option A: A-IV, B-II, C-III, D-I

• Statement I is incorrect. The ground substance of bone is heavily mineralised (mainly hydroxyapatite, a form of calcium phosphate) which makes bone hard and rigid. Although bone resists compression well, it is not described as pliable; pliability is a feature of cartilage, not mineralised bone.

Statement II: "The bone marrow of all bones is the site of production of blood cells."

• Statement II is also incorrect. While red bone marrow is the site of haematopoiesis (production of blood cells), not all bones in an adult contain red marrow. Many long bones in adults contain yellow marrow (mainly fat) which does not actively produce blood cells. Red marrow is confined to specific bones (for example pelvis, ribs, sternum, vertebrae).

Therefore both statements are incorrect and option (b) is correct.

• A - Crop: The crop is a thin-walled storage chamber in the foregut where food is temporarily held after ingestion.
• B - Gizzard (Proventriculus): The gizzard is a muscular, thick-walled region with chitinous plates that grind food mechanically; it lies immediately after the crop.
• C - Hepatic caeca: These are finger-like outpocketings at the foregut–midgut junction that secrete digestive enzymes and increase the surface for digestion and absorption.
• D - Malpighian tubules: These are slender excretory tubules attached near the junction of midgut and hindgut; they remove nitrogenous wastes from the haemolymph and help in osmoregulation.

Hence the labels correspond to (c) A-Crop, B-Gizzard, C-Hepatic caeca, D-Malpighian tubules.

• A. "Bear cilia on their free surface" — this is true for some epithelial types (ciliated epithelium) but it is not a general feature of all epithelium, so A is not universally correct.
• B. Epithelia provide linings of body surfaces and cavities — this is correct.
• C. Compound (stratified) epithelium is multi-layered and mainly provides protection; its role in secretion and absorption is limited — this is correct.
• D. "Located in the tip of the nose" — the tip of the nose is made of cartilage and skin; epithelial tissue lines the nasal cavity but is not the structural tissue of the nose tip. So D is not correct as stated.
• E. Exocrine glands are formed from epithelial tissue and secrete their products via ducts — this is correct.

Therefore, the true features are B, C and E, so option (c) is correct.

• A. Metamorphosis → II (Paurometabolous): Cockroaches show gradual metamorphosis (paurometabolous) where nymphs resemble the adult form and develop gradually.
• B. Brain → IV (Supraoesophageal ganglion): The insect brain is the supra-oesophageal ganglion located above the oesophagus.
• C. Vision → I (Ommatidia): Compound eyes are made up of many ommatidia, each functioning as a light-detecting unit.
• D. Respiration → III (Spiracles): Respiration in cockroach is through openings called spiracles that lead to the tracheal system.

Matching gives A-II, B-IV, C-I, D-III, so option (d) is correct.

• (a) is incorrect — adhering junctions (adhesion belts, desmosomes) primarily provide mechanical attachment between cells and to the extracellular matrix, not direct intercellular communication.
• (b) is correct — tight junctions (zonula occludens) seal adjacent epithelial cells, preventing paracellular leakage of substances across a tissue (e.g., intestinal epithelium).
• (c) is incorrect — cementing and strong mechanical attachment are mainly functions of desmosomes/adhering junctions rather than tight junctions.
• (d) is incorrect — gap junctions provide channels for direct transfer of ions and small molecules between adjacent cells and thus facilitate communication; they do not create gaps between cells.

Hence option (b) is the correct statement.

• A. Collateral gland — present in female cockroach; involved in reproduction (associated with egg-case formation).
• B. Mushroom gland — a male accessory gland; not present in females.
• C. Spermatheca — present in female cockroach; stores sperm after mating.
• D. Anal style — present in both sexes (short styles may be present), but it is not a female-specific reproductive structure.
• E. Phallic gland — male reproductive gland; absent in females.

Therefore, structures present specifically in females among the listed options are A (Collateral gland) and C (Spermatheca), so option (d) is correct.

• A. Cartilage — chondrocytes produce extracellular matrix including collagen fibres (and elastic fibres in elastic cartilage).
• B. Bone — osteoblasts/osteocytes synthesise collagen fibres that form the organic matrix of bone.
• C. Adipose tissue — contains fibroblasts in the connective tissue framework that secrete collagen and elastic fibres around adipocytes.
• D. Blood — a fluid connective tissue; blood cells do not secrete collagen or elastin fibres.
• E. Areolar tissue — loose connective tissue whose fibroblasts secrete collagen and elastic fibres.

So the tissues where cells secrete collagen or elastin are A, B, C and E — option (b).

• A. Squamous epithelium — found lining blood vessels (endothelium) and air sacs; here it corresponds to the walls of blood vessels (III).
• B. Ciliated epithelium — lines fallopian tubes and bronchioles where cilia move particles or ova (IV).
• C. Glandular epithelium — goblet cells of the alimentary canal are unicellular glandular epithelial cells that secrete mucus (I).
• D. Compound epithelium — stratified epithelium found in ducts and protective linings; inner lining of pancreatic ducts matches (II).

Therefore the correct matching is A-III, B-IV, C-I, D-II — option (d).

Ligaments are made of dense regular connective tissue — their collagen fibres are arranged in parallel to resist tension along one direction. So Statement I is incorrect.
Cartilage is a specialised connective tissue composed of chondrocytes in a gel-like matrix; it is not classified as dense regular tissue. So Statement II is incorrect.
Hence both statements are false and option (b) is correct.

Goblet cells are unicellular glandular epithelial cells that secrete mucus.
Earwax (cerumen) is secreted by ceruminous glands, which are modified exocrine glands.
Therefore, both statements are true and option (c) is correct.

• Mast cells (A) — are found in connective tissues (e.g., areolar tissue) and participate in immune responses, matching location II in the list.
• Inner surface of bronchiole (B) — lined by ciliated epithelium (I) to move mucus and trapped particles.
• Blood (C) — is a specialised connective tissue (IV).
• Tubular parts of nephron (D) — lined by cuboidal epithelium, which matches III.

Therefore option (c) is correct.

• Columnar epithelium (A) — lines stomach and intestine (II).
• Ciliated epithelium (B) — lines bronchioles (III).
• Squamous epithelium (C) — forms endothelium (I).
• Cuboidal epithelium (D) — found in ducts of glands (IV).

Thus the correct matching is option (d).

Correct option: B

(a) is correct. Bones provide support to the body framework and protect internal organs (for example, the skull protects the brain and the ribs protect the heart and lungs).

(b) is correct. Limb bones such as the femur and tibia are adapted for weight-bearing and locomotion.

(c) is incorrect. Blood cells are formed by bone marrow (the process of hematopoiesis occurs in marrow); ligaments are fibrous connective tissue that join bones and do not produce blood cells.

(d) is correct. Adipose tissue is specialised for storing fat, serving as an energy reserve and providing insulation and cushioning.

(e) is incorrect. Tendons attach muscle to bone, whereas ligaments connect bone to bone.

Therefore, (a), (b) and (d) are correct and the correct option is B.

Ciliated epithelium lines the inner surface of bronchioles and fallopian tubes; cilia move mucus in the airways and help transport the egg in the female reproductive tract.

Hepatic caeca are involved in the secretion of digestive enzymes and do not participate in excretion.
Urecose glands (in males), Malpighian tubules, and fat bodies are associated with excretory functions in cockroach.
Therefore, option (a) is the correct answer.

• (a) Crop — storage of food (iv).
• (b) Proventriculus (gizzard) — grinding of food (i).
• (c) Hepatic caecae — secretion of digestive enzymes (ii).
• (d) Malpighian tubules — removal of nitrogenous wastes (iii).

• Crop and gizzard are characteristic features of the avian alimentary canal. Therefore birds such as Pavo (peacock), Psittacula (parrot) and Corvus (crow) possess these additional chambers, making option (d) correct.
• Other options include non-avian animals (amphibians, fishes, reptiles, mammals) where crop and gizzard as a pair are not typical.

Tegmina are the leathery forewings of cockroaches and they develop from the mesothorax; the hindwings arise from the metathorax. No wings arise from the prothorax.

Option (d) is the correct answer as neuroglia are a part of nervous tissue.

• Neuroglia (glial cells) are supportive cells of the nervous system and belong to nervous tissue, not connective tissue.
• Adipose tissue, cartilage and blood are all classified as connective tissues (specialised or loose types).

Option (a) is the correct answer because

• Ciliated epithelium lines hollow organs like bronchioles and fallopian tubes to move mucus or ova.
• Some columnar or cuboidal cells are specialised as glandular epithelium (goblet cells are unicellular glands).
• Tendons are dense regular connective tissues attaching muscle to bone.
• Adipose tissue is loose connective tissue that stores fat, often under the skin.

• The smooth muscle fibres taper at both ends (fusiform) and do not show striations.
• The wall of internal organs such as the blood vessels, stomach and intestine contains this type of muscle tissue.
• Smooth muscles are ‘involuntary’ as their functioning cannot be directly controlled.